Histone methylation plays a fundamental role in the organization of chromatin and in the regulation of gene transcription. Our long-term goal is to elucidate how lysine-specific histone methyltransferases regulate gene expression and contribute to cellular development and disease. One such enzyme that is highly conserved in eukaryotes is the histone H3 lysine 36 (H3K36) methyltransferase Set2. We, and others, have shown that Set2 associates with RNA polymerase II during transcription elongation, and that its methylation at H3K36 directs the recruitment of a histone deacetylase complex (Rpd3S) that suppresses inappropriate initiation of transcription. While the basic functions of Set2 have been characterized, little is still known regarding: i) how the Set2 enzyme itself is regulated, ii) whether other functions for this enzyme exist, and iii) how the distinct methylation states of H3K36 (me1, me2, and me3) and their demethylation contribute to chromatin organization and gene transcription. Using Saccharomyces cerevisiae as a model organism, we plan to use a combination of biochemistry and genetics to further address the functions of Set2 and H3K36me in transcriptional regulation and beyond. Our goal will be to address a number of broad questions that will advance our understanding of how histone methyltransferases and demethylases regulate the chromatin environment and contribute to gene expression. These include: 1) How is Set2 targeted to genes and is itself regulated by post- translational modification? 2) How does H3K36 demethylation contribute to the transcription process? 3) Do the different H3K36 methylation states have distinct biological activities in transcription, and does this histone 'mark' function in other DNA- related activities such as DNA repair and replication? These studies will have a significant impact to the field, as our current understanding of histone post-translational modifications, including H3K36 methylation in particular, is very limited. This is underscored by the fact that the dysregulation of enzymes that mediate H3K36 methylation lead to a variety of human diseases including cancer. Given the complexity of having multiple H3K36-methylating enzymes in mammalian cells, yeast affords the exceptional ability to apply genetics and biochemistry to understand the fundamental functions of a highly significant histone 'mark' in chromatin.